Battery with nonaqueous electrolyte

ABSTRACT

The development of a novel negative electrode material has led to the provision of a battery with a nonaqueous electrolyte which has a combination of a high discharge capacity with excellent cycling characteristics. The battery with a nonaqueous electrolyte comprises: a positive electrode; a negative electrode having a negative electrode active material capable of occluding and releasing an alkali metal; and a nonaqueous electrolyte. The negative electrode active material contains at least one element selected from the group consisting of group 4B elements and group 5B elements and has at least one crystal structure selected from the group consisting of BiF 3  structure, Cu 2 MnAl structure, and AgAsMg structure. And the negative electrode active material contains at least one element selected from the group consisting of Al, Si, Ge, Sn, P, Sb and Bi and has at least one crystal structure selected from the group consisting of BiF 3  structure, Cu 2 MnAl structure, and AgAsMg structure.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a battery with a nonaqueouselectrolyte, and more particularly to a battery with a nonaqueouselectrolyte, using an improved negative electrode active material.

[0003] 2. Discussion of the Background

[0004] In recent years, rechargeable batteries with a nonaqueouselectrolyte, using a lithium metal, a lithium alloy, a lithium compound,a carbon material or the like as a negative electrode active materialhave been expected as batteries with high energy density, and theresearch and development of these batteries are currently beingenergetically done. Up to now, lithium ion batteries using LiCoO₂,LiMn₂O₄ or the like as the positive electrode active material and acarbon material, capable of occluding and releasing lithium, as thenegative electrode active material have been extensively put topractical use.

[0005] On the other hand, rechargeable batteries using a lithium metal,a lithium alloy, or a lithium compound as the negative electrode activematerial have been expected to have high capacity. They, however, havenot yet been put to practical use. The reason for this is mainly thatthe use of the lithium metal leads to a deterioration of lithium as aresult of a reaction of a nonaqueous electrolysis solution with thelithium metal and, in addition, the elimination of lithium due to theoccurrence of dendritic lithium upon the repetition of discharge andcharge and thus poses problems of internal short circuit and short cyclelife. In order to solve these problems, studies have been made on theuse of lithium alloys or lithium compounds as the negative electrode. Inparticular, in lithium-aluminum or other alloys, the reactivity with thenonaqueous electrolysis solution can be reduced to improve the chargeand discharge efficiency. In this case, however, the repetition of ahigh level of discharge and a high level of charge causes crumbling ofthe electrode. Therefore, an improvement in cycle life characteristicsis unsatisfactory.

[0006] Further, the use of chalcogen compounds, such as oxides, as thenegative electrode active material has been proposed from the viewpointof increasing the capacity in the negative electrode (for example, SnOand SnO₂; see Japanese Patent Laid-Open Nos. 122274/1995). Further, aproposal has been made to use amorphous oxides, such as SnSiO₃ orSnSi_(1-x)P_(x)O₃, to improve cycle characteristics (see Japanese PatentLaid-Open No. 288123/1995). At the present time, however, even thesechalcogen compounds could not have simultaneously improved the cyclelife characteristics and the capacity to a satisfactory level.

SUMMARY OF THE INVENTION

[0007] The present invention has been made with a view to solving theabove problem of the prior art, and it is an object of the presentinvention to provide a battery with a nonaqueous electrolyte, whichpossesses a combination of high capacity with excellent cycle life,through the use of a negative electrode active material possessing ahigh capacity and excellent charge-discharge cycle characteristics.

[0008] According to one aspect of the present invention, there isprovided a battery with a nonaqueous electrolyte, comprising: a positiveelectrode; a negative electrode having a negative electrode activematerial capable of occluding and releasing an alkali metal; and anonaqueous electrolyte, said negative electrode active materialcontaining at least one element selected from the group consisting ofgroup 4B elements and group 5B elements and having at least one crystalstructure selected from the group consisting of BiF₃ structure, Cu₂MnAlstructure, and AgAsMg structure. Above 4B elements and group 5B elementsare selected from the group consisting of Si, Ge, Sn, P, Sb and Bi.Since Al does so the same effect as Sb, it can be replaced with andadopted as Sb. So the negative electrode can be contained the activematerial, the active material containing at least one element selectedfrom the group consisting of Al, Si, Ge, Sn, P, Sb and Bi, and theactive material having at least one crystal structure selected from thegroup consisting of BiF₃ structure, Cu₂MnAl structure and AgAsMgstructure.

[0009] According to an embodiment of the present invention, the negativeelectrode active material further contains an alkali metal.

[0010] The above negative electrode active material can occlude a largeamount of an alkali metal such as lithium, and, at the same time, hashigh reversibility between an occlusion reaction and a release reactionand can solve the problem of crumbling involved in charge-dischargecycles. Thus, this negative electrode active material can realize anegative electrode possessing a long life and a high capacity. Theseadvantageous characteristics are derived from the fact that the negativeelectrode active material according to the present invention is astructurally stable material which, even after the occlusion of a largeamount of an alkali metal, can maintain the basic crystal structure.

[0011] In particular, from the viewpoints of both high capacity and longlife, the crystal structure preferably comprises at least one memberselected from the group consisting of BiF₃ structure, Cu₂MnAl structure,and AgAsMg structure, and, more preferably, the negative electrodeactive material further contains an alkali metal from the viewpoint oflong service life.

[0012] Further, at least one element selected from the group consistingof Al, Si, Ge, Sn, P, Sb and Bi is preferably contained from theviewpoint of high capacity. In particular, the negative electrode activematerial preferably contains antimony as an indispensable component.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a partially sectional view showing an embodiment of arechargeable lithium battery (a cylindrical rechargeable lithiumbattery) according to the present invention; and

[0014]FIGS. 2 and 3 are photomicrographs of particles of a negativeelectrode active material (Ni₂MnSb) (magnification: 3000 times).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The rechargeable battery with a nonaqueous electrolyte (forexample, a cylindrical rechargeable battery with a nonaqueouselectrolyte) according to the present invention will be described withreference to FIG. 1.

[0016]FIG. 1 shows an embodiment of a rechargeable battery with anonaqueous electrolyte according to the present invention. In thisbattery, for example, an insulator 2 is disposed at the bottom of aclosed-end cylindrical container 1 made of stainless steel. A group ofelectrodes 3 are housed in the container 1. The group of electrodes 3have a structure such that a strip formed by stacking the positiveelectrode 4, the separator 5, the negative electrode 6, and theseparator in that order on top of one another is spirally wound in sucha manner that the separator 5 is located outermost.

[0017] An electrolysis solution is placed within the container 1. Aninsulating paper 7 having an opening in its center is disposed above thegroup of electrodes 3 within the container 1. An insulating seal plate 8is disposed in an upper opening in the container 1, and is fixed to thecontainer 1 by inwardly crimping a portion around the upper opening. Apositive electrode terminal 9 is fitted into the center of theinsulating seal plate 8. One end of a positive electrode lead 10 isconnected to the positive electrode 4 with the other end being connectedto the positive electrode terminal 9. The negative electrode 6 isconnected to the container 1 as the negative electrode terminal througha negative electrode lead (not shown)

[0018] Next, the positive electrode 4, the separator 5, the negativeelectrode 6, and the nonaqueous electrolyte will be described in moredetail.

[0019] 1) Positive Electrode 4

[0020] The positive electrode 4 may be prepared by suspending a positiveelectrode active material, a conductive agent, and a binder in asuitable solvent, coating the suspension onto a current collector, suchas an aluminum foil, drying the coated current collector, and pressingthe dried, coated current collector into a strip electrode.

[0021] Various oxides and sulfides are usable as the positive electrodeactive material, and examples thereof include: manganese dioxide (MnO₂),lithium manganese composite oxides (for example, LiMn₂O₄ or LiMnO₂),lithium nickel composite oxides (for example, LiNiO₂), lithium cobaltcomposite oxides (for example, LiCoO₂), lithium nickel cobalt compositeoxides (for example, LiNi_(1-x)Co_(x)O₂), lithium manganese cobaltcomposite oxides (for example, LiMn_(x)Co_(1-x)O₂) and vanadium oxides(for example, V₂O₅). Further, organic materials such as electricallyconductive polymer materials and disulfide polymer materials may also beused. Lithium manganese composite oxide (LiMn₂O₄), lithium nickelcomposite oxide (LiNiO₂), lithium cobalt composite oxide (LiCoO₂),lithium nickel cobalt composite oxide (LiNi_(0.8)Co_(0.2)O₂), lithiummanganese cobalt composite oxides (LiMn_(x)Co_(1-x)O₂) and the like aremore preferred positive electrodes from the viewpoint of high batteryvoltage.

[0022] Examples of conductive agents usable herein include acetyleneblack, carbon black, and graphite.

[0023] Examples of binders usable herein include polytetrafluoroethylene(PTFE), polyvinylidene fluoride (PVdF), and fluororubber.

[0024] The mixing ratio of the positive electrode active material to theconductive agent to the binder is preferably 80 to 95% by weight of thepositive electrode active material: 3 to 20% by weight of the conductiveagent: 2 to 7% by weight of the binder.

[0025] 2) Separator 5

[0026] The separator 5 may be formed of, for example, a nonwoven fabricof synthetic resin, a porous film of polyethylene, or a porous film ofpolypropylene.

[0027] 3) Negative Electrode 6

[0028] The negative electrode 6 may be prepared by suspending aconductive agent and a binder in a suitable solvent, coating thesuspension onto a metal foil, such as a copper foil, drying the coatedfoil, and pressing the dried, coated foil to form a strip electrode.

[0029] A part of the negative electrode active material is constitutedby a material which comprises at least one member selected from thegroup consisting of Al, Si, Ge, Sn, P, Sb and Bi and has at least onecrystal structure selected from the group consisting of BiF₃ structure,Cu₂MnAl structure, and AgAsMg structure.

[0030] Preferably, at least one member selected from the groupconsisting of Al, Si, Ge, Sn, P, Sb and Bi is used from the viewpoint oflong life and high capacity. In particular, the negative electrodeactive material preferably contains antimony as an indispensablecomponent. In this connection, it should be noted that carbon isunfavorable because any desired crystal structure cannot be formed.

[0031] The negative electrode active material having Cu₂MnAl structureis preferably at least one member selected from the group consisting ofNi₂MnSb, Co₂MnSb, Ni₂MgSb, and Co₂MgSb.

[0032] A preferred specific example of the negative electrode activematerial having AgAsMg structure is at least one member selected fromthe group consisting of FeVSb, CoTiSb, NiTiSb, NiNbSb, CoNbSb, NiVSb,CoVSb, CuMgSb, NiMnSb, CoMnSb, NiMgSb, and CoMgSb.

[0033] Further, a preferred specific example of the negative electrodeactive material having BiF₃ structure is at least one member selectedfrom the group consisting of Ni₃Sn, Co₃Sn, Fe₃Al, and Fe₃Si.

[0034] The above negative electrode active material can occlude a largeamount of an alkali metal such as lithium, and, at the same time, hashigh reversibility between an occlusion reaction and a release reactionand can solve the problem of crumbling involved in charge-dischargecycles. Thus, this negative electrode active material can realize anegative electrode possessing a long life and a high capacity. Theseadvantageous characteristics are probably derived from the fact that thenegative electrode active material according to the present invention isa structurally stable material which, even after the occlusion of alarge amount of an alkali metal, can maintain the basic crystalstructure.

[0035] In particular, from the viewpoints of both high capacity and longlife, the crystal structure preferably comprise at least one memberselected from the group consisting of BiF₃ structure, Cu₂MnAl structure,and AgAsMg structure, and, more preferably, the negative electrodeactive material further contains an alkali metal from the viewpoint oflong life.

[0036] The AgAsMg structure is a structure belonging to cF12 of PearsonSymbol. CaF₂ structure also belongs to cF12. Compounds having CaF₂structure, such as CoSi₂, NiSi₂, Mg₂Si, and Mg₂Sn, can occlude alkalimetals, such as lithium, and, as with compounds having AgAsMg structureaccording to the present invention, can be utilized as a high-capacitynegative electrode active material. Rather, many compounds having CaF₂structure have higher capacity than the compounds having AgAsMgstructure according to the present invention In the case of thecompounds having CaF₂ structure, however, at the time of occlusion andrelease of lithium, the crystal lattice undergoes a significant changein volume, and the repetition of charge and discharge causesdisintegration of the crystal and thus results in significantlydeteriorated cycle life. This makes it difficult to practically usethese compounds. On the other hand, the compounds having AgAsMgstructure according to the present invention have an advantageousfeature such that they can moderately occlude lithium and undergo nosignificant change in volume and thus possesses excellent cycle lifecharacteristics.

[0037] The BiF₃ structure and the Cu₂MnAl structure belong to cF16 ofPearson Symbol. NaTl structure also belong to cF16. Compounds havingNaTl structure include lithium alloys such as AlLi, CdLi, and GaLi. Asdescribed above, these lithium alloys are known as negative electrodeactive materials having very high capacity. However, as with thecompounds having CaF₂ structure, these compounds have a problem that achange in volume of crystal at the time of charge and discharge is solarge that the cycle life characteristics are deteriorated. By contrast,compounds having BiF₃ structure and the Cu₂MnAl structure according tothe present invention can occlude a suitable amount of lithium andundergo no significant change in volume and thus advantageously possessexcellent cycle life characteristics.

[0038] Further, at least one element selected from the group consistingof Al, Si, Ge, Sn, P, Sb and Bi is preferably contained from theviewpoint of high capacity. The incorporation of antimony as anindispensable component is particularly preferred.

[0039] The reason why the presence of antimony as the indispensablecomponent in the negative electrode active material is advantageous isas follows.

[0040] The negative electrode active material according to the presentinvention may be formed, for example, by arc melting, high frequencymelting, mechanical alloying, CVD, and sputtering, and the method forforming the negative electrode active material is not particularlylimited. Among others, the production of the negative electrode activematerial using a solid phase reaction is advantageous in that ahigh-performance negative electrode active material can be simplyproduced. This method comprises the steps of mixing powders of elementsfor constituting the compound together and heat treating the mixedpowder to cause a solid phase reaction, thereby giving a contemplatedcompound.

[0041] In this case, the heat treatment temperature is preferably belowthe melting points of the elements for constituting the compound.According to the finding of the present inventor, heat treatment at atemperature of the melting point of the constituent elements or abovehas a fear that, after melting and solidification steps, a secondcompound other than the contemplated compound is contained as animpurity phase. Further, in this case, the synthesized compound islikely to be bulky. Therefore, in use of the compound as the negativeelectrode active material, this compound should be pulverized. However,it has been found that powder particles produced by pulverization areparticles having smooth surface which have a small specific surface areaand, upon a change in volume, are less likely to relieve strain. FIG. 2is a photomicrograph (magnification: 3000 times) of particles of acompound (Ni₂MnSb) which has been produced at the melting point of theconstituent elements or above and has been pulverized as describedabove.

[0042] On the other hand, it has been found that, when the heattreatment is carried out at a temperature which does not melt theconstituent elements, that is, at a temperature below the melting pointof the element having the lowest melting point in the constituentelements, a compound is synthesized by a complete solid phase reaction,resulting in the formation of good fine particles of the compound. FIG.3 is a photomicrograph (magnification: 3000 times) of particles of acompound (Ni₂MnSb) which has been produced at a temperature below themelting point of the constituent elements. As can be seen from FIG. 3, apowder is obtained which comprises primary particles of 0.05 to 2 μmconnected to one another like a bunch of grapes. The compound in thisform has a high specific surface area and can effectively relieve straincaused by a change in volume. This is also advantageous in that thedisintegration of the particle form can be prevented.

[0043] For this reason, the negative electrode active material accordingto the present invention is preferably produced in a synthesistemperature region which does not melt the constituent elements. Whenthis is taken into consideration, among the Al, Si, Ge, Sn, P, Sb and Bithe Si have an excessively high melting point which leads to synthesisat a relatively high reaction rate and thus makes it difficult tosynthesize the compound in a form as shown in FIG. 3. On the contrary,tin, bismuth, phosphorus and the like have excessively low melting pointwhich leads to synthesis at a low reaction rate and thus, here again,makes it difficult to synthesize the compound in a form as shown in FIG.3. On the other hand, antimony has a melting point of about 630° C.which can realize an ideal reaction rate and advantageously enables thecompound in a form as shown in FIG. 3 to be easily synthesized.Therefore, the incorporation of antimony as an indispensable componentinto the negative electrode active material according to the presentinvention is particularly preferred from the technical viewpoint of theabove-described production method.

[0044] Both FIGS. 2 and 3 show the results of synthesis of Ni₂MnSb.However, FIGS. 2 and 3 are different from each other in that FIG. 2shows a product which has been synthesized at 850° C., that is, atemperature above the melting point of antimony, while FIG. 3 shows aproduct which has been synthesized at 550° C., that is, a temperaturebelow the melting point of antimony. As can be seen from FIGS. 2 and 3,the surface of particles synthesized at 850° C. is smooth and has asmall specific surface area, while particles synthesized at 550° C. areconstituted by aggregates (secondary particles) of small primaryparticles and have a large specific surface area.

[0045] According to the present invention, when the battery is arechargeable battery with a nonaqueous electrolyte, the use of amaterial, into which an alkali metal (for example, lithium) has beenpreviously incorporated, for example, LiCoO₂, LiMnO₂, or LiNiO₂, as apositive electrode permits the alkali metal (for example, lithium) tomigrate from the positive electrode to the material according to thepresent invention at the time of initial charge of the battery and,thereafter, permits the material of the present invention to reversiblyocclude and release the alkali metal to function as a negative electrodeof the rechargeable battery. Further, in order to stabilize thecharge-discharge cycles, the use of an alkali metal-containing materialas a negative electrode active material is preferred even when thealkali metal-containing material is used as the positive electrode. Whena material, into which an alkali metal has not been previouslyincorporated, for example, CoO₂, MnO₂, or NiO₂, is used as the positiveelectrode active material, a method may be adopted wherein a material,into which an alkali metal has been previously incorporated, is used asthe negative electrode active material, or alternatively a laminate ofan alkali metal and an alkali metal-free material according to thepresent invention is used to electrochemically produce an alkalimetal-containing material.

[0046] When the battery is a primary battery of a battery with anonaqueous electrolyte, it is preferred to use as a positive electrode amaterial into which an alkali metal has not been previouslyincorporated, while an alkali metal-containing material is used as thenegative electrode.

[0047] The negative electrode active material preferably has an averageparticle diameter (an average diameter of secondary particles) in therange of 0.1 to 100 μm.

[0048] The negative electrode active material may be produced by mixingpowders as a starting material together so as to provide a predeterminedstochiometric amount ratio and heat treating the mixture at atemperature of 400 to 1200° C. in an inert gas atmosphere, a reducingatmosphere or in vacuo. When the heat treatment is carried out at atemperature below 400° C., the time necessary for the compound to beproduced by the reaction is long, leading to poor productivity. On theother hand, a high temperature above 1200° C. cause significantdissipation due to evaporation of an atom having high vapor pressure,such as antimony, which results in a significant change in compositionfrom the time when the powders are mixed together.

[0049] Conductive agents usable herein include, for example, acetyleneblack, carbon black, and graphite.

[0050] Binders usable herein include, for example,polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF),fluororubber, ethylene-butadiene rubber (SBR), andcarboxymethylcellulose (CMC).

[0051] The mixing ratio of the negative electrode active material to theconductive agent to the binder is preferably 70 to 95% by weight of thenegative electrode active material: 0 to 25% by weight of the conductiveagent: 2 to 10% by weight of the binder.

[0052] 4) Nonaqueous Electrolyte

[0053] Nonaqueous electrolytes usable herein include a liquidelectrolyte prepared by dissolving an electrolyte in a nonaqueoussolvent, a polymeric gel-like electrolyte prepared by incorporating thenonaqueous solvent and the electrolyte into a polymeric material, apolymeric solid electrolyte containing the electrolyte alone, and alithium ion-conductive inorganic solid electrolyte.

[0054] A nonaqueous solvent prepared by dissolving a lithium salt as anelectrolyte in a nonaqueous solvent in a lithium battery may be used asthe liquid electrolyte. In this case, preferred is a nonaqueous solventcomposed mainly of a cyclic carbonate, such as ethylene carbonate (EC)or propylene carbonate (PC), or a nonaqueous solvent composed mainly ofa mixed solvent comprised of the cyclic carbonate and a nonaqueoussolvent having a lower viscosity than the cyclic carbonate (hereinafterreferred to as “second solvent”).

[0055] Examples of the second solvent include: linear carbonates, suchas dimethyl carbonate, methylethyl carbonate, and diethyl carbonate;γ-butyrolactone; acetonitrile; methyl propionate; ethyl propionate;cyclic ethers, such as tetrahydrofuran and 2-methyltetrahydrofuran; anlinear ethers, such as dimethoxyethane and diethoxyethane.

[0056] Alkali salts, particularly lithium salts, may be mentioned as theelectrolyte. Lithium salts include lithium phosphate hexafluoride(LiPF₆), lithium borofluoride (LiBF₄), arsenic lithium hexafluoride(LiAsF₆), lithium perchlorate (LiClO₄), and lithiumtrifluoromethanesulfonate (LiCF₃SO₃). Among them, lithium phosphatehexafluoride (LiPF₆) and lithium borofluoride (LiBF₄) are particularlypreferred. The solubility of the electrolyte in the nonaqueous solventis preferably 0.5 to 2.0 moles/liter.

[0057] The gel-like electrolyte is one prepared by dissolving thesolvent and the electrolyte in a polymeric material to form a gel.Polymeric materials usable herein include polyacrylonitrile,polyacrylate, polyvinylidene fluoride (PVdF) and polyethylene oxide(PEO), or copolymers of monomers constituting the above polymers withother monomers.

[0058] The solid electrolyte is one prepared by dissolving theelectrolyte in a polymeric material to form a solid. Polymeric materialsusable herein include polyacrylonitrile, polyvinylidene fluoride (PVdF)and polyethylene oxide (PEO), or copolymers of monomers constituting theabove polymers with other monomers. Inorganic solid electrolytes includelithium-containing ceramic materials. Among others, Li₃N, Li₃PO₄—Li₂Sglass and the like may be mentioned as the inorganic solid electrolyte.

[0059] In FIG. 1, an embodiment of the present invention is shownwherein the present invention has been applied to a cylindrical batterywith a nonaqueous electrolyte. Likewise, the present invention can befurther applied to batteries in other forms, for example, polygonalbatteries with a nonaqueous electrolyte and button batteries with anonaqueous electrolyte. The group of electrodes housed in the containerof the battery are not limited to a spiral form, and may be in the formof a stack prepared by stacking a plurality of units on top of the otheror one another, each unit composed of a positive electrode, a separator,and a negative electrode stacked in that order.

EXAMPLES

[0060] Examples of the present invention will be described withreference to FIG. 1. However, it should be noted that the presentinvention is not limited to these examples only so far as modificationsand variations fall within the scope of the present invention.

Example 1

[0061] <Preparation of Positive Electrode>

[0062] 91% by weight of a lithium cobalt oxide (LiCoC₂) powder as apositive electrode active material, 2.5% by weight of acetylene black,3% by weight of graphite, and 4% by weight of polyvinylidene fluoride(PVdF) were added to and mixed with an N-methylpyrrolidone (NMP)solution. The mixture was coated on a 15 μm-thick aluminum foil as acurrent collector. The coated aluminum foil was dried, followed bypressing to prepare a positive electrode having an electrode density of3.0 g/cm³.

[0063] <Preparation of Negative Electrode>

[0064] A nickel powder having a purity of 99% and an average particlediameter of 20 μm, a manganese powder having a purity of 99% and anaverage particle diameter of 20 μm, and an antimony powder having apurity of 99.9% and an average particle diameter of 20 μm were mixedtogether so as to provide an atomic equivalent ratio of 2:1:1. Themixture was thoroughly stirred by means of a V mixer. The thoroughlystirred mixed powder was filled into an alumina crucible, and was thenheat treated under an argon gas stream at 600° C. for 120 hr, wherebythese powders were allowed to react with one another. The materialobtained by the heat treatment was analyzed by XRD. As a result, only apeak attributable to an Ni₂MnSb phase having Cu₂MnAl structure wasobserved, indicating that this material is constituted by a single phaseof Ni₂MnSb. The reaction product as an aggregate was ground in an agatemortar to prepare an Ni₂MnSb powder having an average particle diameterof 20 μm. 5% by weight of graphite, 3% by weight of acetylene black, 7%by weight of PVdF, and an NMP solution were added to and mixed with 85%by weight of the Ni₂MnSb powder. The mixture was coated on a currentcollector of a 12 μm-thick copper foil. The coated copper foil wasdried, followed by pressing to prepare a negative electrode.

[0065] <Preparation of Group of Electrodes>

[0066] The positive electrode, a separator formed of a porous film ofpolyethylene, the negative electrode, and the separator were stacked inthat order on top of one another, and the stack was spirally wound sothat the negative electrode was located outermost. Thus, a group ofelectrodes was prepared.

[0067] <Preparation of Nonaqueous Electrolysis Solution>

[0068] Lithium phosphate hexafluoride (LiPF₆) was dissolved in a mixedsolvent composed of ethylene carbonate (EC) and methyl ethyl carbonate(MEC) (mixing volume ratio=1:2) to a concentration of 1.0 mole/liter toprepare a nonaqueous electrolyte.

[0069] The group of electrodes and the electrolysis solution were housedin a closed-end cylindrical stainless steel container to assemble acylindrical rechargeable battery with a nonaqueous electrolyte as shownin FIG. 1.

Examples 2 to 35 and Comparative Examples 1 to 12

[0070] The procedure of Example 1 was repeated, except that negativeelectrode active materials described in Table 1 were used instead of thenegative electrode active material in Example 1. Thus, rechargeablebatteries with a nonaqueous electrolyte of Examples 2 to 35 andComparative Examples 1 to 12 were assembled.

[0071] For the batteries of Examples 1 to 35 and Comparative Examples 1to 12, 0.5 C constant voltage (3.5 V) charge was carried out for 3 hr,and the capacity at 0.5 C discharge (discharge termination voltage=2.0V) was then determined. The number of cycles necessary for the capacityto be reduced to 80% of the capacity of the first cycle was determinedas the cycle life. The results are summarized in Table 1. TABLE 1Negative electrode Ex., active Discharge Cycle life, Comp. Ex. materialcapacity, mAh times Ex. 1 Ni₂MnSb 850 530 Ex. 2 Co₂MnSb 700 570 Ex. 3Ni₂MnSb_(0.8)Bi_(0.2) 870 500 Ex. 4 Co₂MnSb_(0.8)Bi_(0.2) 720 510 Ex. 5Ni₂MnSb_(0.8)P_(0.2) 780 520 Ex. 6 Co₂MnSb_(0.8)P_(0.2) 700 550 Ex. 7Ni₂MnSb_(0.8)Al_(0.2) 710 520 Ex. 8 Co₂MnSb_(0.8)Al_(0.2) 700 540 Ex. 9Ni₂MgSb 800 500 Ex. 10 Co₂MgSb 700 525 Ex. 11 FeVSb 1000 500 Ex. 12NiTiSb 1000 520 Ex. 13 CoTiSb 1000 500 Ex. 14 NiNbSb 900 510 Ex. 15CoNbSb 900 500 Ex. 16 NiVSb 1000 510 Ex. 17 CoVSb 1000 500 Ex. 18 CuMgSb1000 470 Ex. 19 NiMnSb 1200 500 Ex. 20 CoMnSb 1200 490 Ex. 21 NiMgSb1100 480 Ex. 22 CoMgSb 1100 475 Ex. 23 NiTiSn 1200 490 Ex. 24 CoTiSn1200 480 Ex. 25 NiTiSn_(0.8)Si_(0.2) 1100 480 Ex. 26CoTiSn_(0.8)Si_(0.2) 1100 460 Ex. 27 NiTiSn_(0.8)Ge_(0.2) 1150 490 Ex.28 CoTiSn_(0.8)Ge_(0.2) 1150 470 Ex. 29 LiNi₂MnSb 1100 550 Ex. 30Li_(0.1)Co₂MnSb 900 600 Ex. 31 Ni₃Sn 800 500 Ex. 32 Co₃Sn 700 550 Ex. 33Mn₃Si 700 500 Ex. 34 Fe₃Si 800 450 Ex. 35 Fe₃Al 700 450 Comp. Ex. 1 Al1000 150 Comp. Ex. 2 Sn 1300 100 Comp. Ex. 3 SnO 780 50 Comp. Ex. 4 SnO₂700 80 Comp. Ex. 5 Sb 1200 120 Comp. Ex. 6 Bi 1200 150 Comp. Ex. 7 Li1400 80 Comp. Ex. 8 Li—Al 1200 120 Comp. Ex. 9 NiSi₂ 1300 50 Comp. Ex.10 CoSi₂ 1200 75 Comp. Ex. 11 Mg₂Si 1600 30 Comp. Ex. 12 Mg₂Sn 1500 35

[0072] As is apparent from the results, the negative electrode activematerials according to the present invention can provide rechargeablebatteries with a nonaqueous electrolyte which have a high capacity and,at the same time, have excellent charge-discharge cycle characteristics.

[0073] As described above, the present invention can provide batterieswith a nonaqueous electrolyte which are improved in both dischargecapacity and service life, that is, have high discharge capacity and, atthe same time, have prolonged service life.

What is claimed is:
 1. A battery with a nonaqueous electrolyte,comprising: a positive electrode; a negative electrode having a negativeelectrode active material capable of occluding and releasing an alkalimetal, said negative electrode active material containing at least oneelement selected from the group consisting of Al, Si, Ge, Sn, P, Sb andBi and having at least one crystal structure selected from the groupconsisting of BiF₃ structure, Cu₂MnAl structure and AgAsMg structure;and a nonaqueous electrolyte.
 2. The battery with a nonaqueouselectrolyte according to claim 1 , wherein the negative electrode activematerial further contains an alkali metal.
 3. The battery with anonaqueous electrolyte according to claim 1 , wherein the positiveelectrode contains an alkali metal.
 4. The battery with a nonaqueouselectrolyte according to claim 1 , wherein the negative electrode activematerial having Cu₂MnAl structure is at least one member selected fromthe group consisting of Ni₂MnSb, Co₂MnSb, Ni₂MgSb, and Co₂MgSb.
 5. Thebattery with a nonaqueous electrolyte according to claim 1 , wherein thenegative electrode active material having AgAsMg structure is at leastone member selected from the group consisting of FeVSb, CoTiSb, NiTiSb,NiNbSb, CoNbSb, NiVSb, CoVSb, CuMgSb, NiMnSb, CoMnSb, NiMgSb, andCoMgSb.
 6. The battery with a nonaqueous electrolyte according to claim1 , wherein the negative electrode active material is a compound whichhas been synthesized at a temperature below the melting point ofantimony.
 7. The battery with a nonaqueous electrolyte according toclaim 1 , wherein the negative electrode active material is in the formof agglomerates of primary particles with a size of 0.05 to 2 μm.
 8. Thebattery with a nonaqueous electrolyte according to claim 7 , wherein thenegative electrode active material has an average particle diameter of0.1 to 100 μm (in terms of secondary particles).
 9. The battery with anonaqueous electrolyte according to claim 1 , wherein the negativeelectrode active material having BiF₃ structure is at least one memberselected from the group consisting of Ni₃Sn, Co₃Sn, Fe₃Al, and Fe₃Si.10. The battery with a nonaqueous electrolyte according to claim 1 ,wherein the negative electrode contains, as a conductive agent, at leastone member selected from the group consisting of acetylene black, carbonblack, graphite, and mixtures of these materials.
 11. The battery with anonaqueous electrolyte according to claim 10 , wherein the negativeelectrode comprises a binder comprising one member selected from thegroup consisting of polytetrafluoroethylene (PTFE), polyvinylidenefluoride (PVdF), fluororubber, ethylene-butadiene rubber (SBR),carboxymethylcellulose (CMC), and mixtures of these materials.
 12. Thebattery with a nonaqueous electrolyte according to claim 10 , whereinthe mixing ratio of the negative electrode active material to theconductive agent to the binder is 70 to 95% by weight of the negativeelectrode active material: 0 to 25% by weight of the conductive agent: 2to 10% by weight of the binder.
 13. A battery with a nonaqueouselectrolyte, comprising: a positive electrode; a negative electrodehaving a negative electrode active material capable of occluding andreleasing an alkali metal, said negative electrode active materialcomprising antimony as an indispensable component and having at leastone crystal structure selected from the group consisting of BiF₃structure, Cu₂MnAl structure and AgAsMg structure; and a nonaqueouselectrolyte.
 14. The battery with a nonaqueous electrolyte according toclaim 13 , wherein the negative electrode active material furthercontains an alkali metal.
 15. The battery with a nonaqueous electrolyteaccording to claim 13 , wherein the positive electrode contains analkali metal.
 16. The battery with a nonaqueous electrolyte according toclaim 13 , wherein the negative electrode active material having Cu₂MnAlstructure is at least one member selected from the group consisting ofNi₂MnSb, Co₂MnSb, Ni₂MgSb, and Co₂MgSb.
 17. The battery with anonaqueous electrolyte according to claim 13 ; wherein the negativeelectrode active material having AgAsMg structure is at least one memberselected from the group consisting of FeVSb, CoTiSb, NiTiSb, NiNbSb,CoNbSb, NiVSb, CoVSb, CuMgSb, NiMnSb, CoMnSb, NiMgSb, and CoMgSb. 18.The battery with a nonaqueous electrolyte according to claim 13 ,wherein the negative electrode active material is a compound which hasbeen synthesized at a temperature below the melting point of antimony.19. The battery with a nonaqueous electrolyte according to claim 13 ,wherein the negative electrode active material is in the form ofagglomerates of primary particles with a size of 0.05 to 2 μm.
 20. Thebattery with a nonaqueous electrolyte according to claim 19 , whereinthe negative electrode active material has an average particle diameterof 0.1 to 100 μm (in terms of secondary particles).
 21. The battery witha nonaqueous electrolyte according to claim 13 , wherein the negativeelectrode contains, as a conductive agent, at least one member selectedfrom the group consisting of acetylene black, carbon black, graphite,and mixtures of these materials.
 22. The battery with a nonaqueouselectrolyte according to claim 21 , wherein the negative electrodecomprises a binder comprising one member selected from the groupconsisting of polytetrafluoroethylene (PTFE), polyvinylidene fluoride(PVdF), fluororubber, ethylene-butadiene rubber (SBR),carboxymethylcellulose (CMC), and mixtures of these materials.
 23. Thebattery with a nonaqueous electrolyte according to claim 22 , whereinthe mixing ratio of the negative electrode active material to theconductive agent to the binder is 70 to 95% by weight of the negativeelectrode active material: 0 to 25% by weight of the conductive agent: 2to 10% by weight of the binder.
 24. A battery with a nonaqueouselectrolyte, comprising: a positive electrode; a negative electrodehaving a negative electrode active material capable of occluding andreleasing an alkali metal, said negative electrode active materialcontaining at least one element selected from the group consisting ofgroup 4B elements and group 5B elements and having at least one crystalstructure selected from the group consisting of BiF₃ structure, Cu₂MnAlstructure and AgAsMg structure; and a nonaqueous electrolyte.
 25. Thebattery with a nonaqueous electrolyte according to claim 24 , whereinthe negative electrode active material further contains an alkali metal.